Percent Solution Calculator
Choose weight/volume, weight/weight or volume/volume percent, say which quantity you need — solute, percent or total solution — and get the answer with the working and a recipe. Add a formula to convert the percent to molarity. Free, no sign-up.
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Results
4.5 g
Amount of solute
0.90% w/v
Percent
500 mL
Amount of solution
0.15 mol/L
Molarity
The working
% w/v = (g of solute ÷ mL of solution) × 100
0.9% = (4.5 g ÷ 500 mL) × 100
Solute per litre of solution: 0.9 × 10 = 9.00 g/L
Molarity = 9.00 g/L ÷ 58.44 g/mol = 0.15 mol/L
How to make it
Dissolve 4.5 g of solute in less than 500 mL of solvent, then add solvent up to a total volume of 500 mL.
How to Use the Percent Solution Calculator
- 1. Pick the type of percent. % w/v is grams of solute per 100 mL of solution, % w/w is grams per 100 g of solution, and % v/v is millilitres of solute per 100 mL of solution.
- 2. Choose what to solve for. The amount of solute to weigh or measure is the usual question; you can also find the percent of a solution you have made, or the total amount of solution a given amount of solute will make.
- 3. Enter the other two quantities. Units can be chosen separately for the solute and the solution (mg, g, kg; µL, mL, L).
- 4. Optionally convert to molarity. Tick the box and give the formula or molar mass. A % w/w solution also needs its density, and a % v/v solution needs the density of the pure solute.
The Percent Solution Formulas
% w/v
(g of solute ÷ mL of solution) × 100
% w/w
(g of solute ÷ g of solution) × 100
% v/v
(mL of solute ÷ mL of solution) × 100
In every case the denominator is the whole finished solution — solute plus solvent — not the solvent alone. A 5% w/w solution is 5 g of solute in 100 g of solution, which means 95 g of solvent. Rearranged, the solute needed is the percent ÷ 100 × the amount of solution.
Worked Examples
% w/v (the default inputs). Normal saline is 0.90% NaCl w/v. For 500.0 mL you need 0.90 ÷ 100 × 500.0 = 4.5 g of NaCl, dissolved and made up to 500.0 mL. As a molarity, 0.90% w/v is 9.0 g/L, and 9.0 ÷ 58.44 = 0.154 mol/L; the calculator shows 0.15 mol/L because 0.90 has two significant figures.
% w/w. Dissolving 5.0 g of sodium chloride in 95.0 g of water gives 100.0 g of solution, so the concentration is 5.0 ÷ 100.0 × 100 = 5.0% w/w.
% v/v. For 250.0 mL of 75.0% v/v ethanol you need 75.0 ÷ 100 × 250.0 = 187.5 mL of ethanol, which the calculator shows as 188 mL, then solvent up to the 250.0 mL mark. Do not simply add 62.5 mL of water: ethanol and water contract when mixed, so the volumes are not additive.
Percent to molarity with a density. Concentrated hydrochloric acid is about 37% w/w with a density of roughly 1.19 g/mL. One litre weighs 1,190 g and holds 37% of that, which is 37 × 10 × 1.19 = 440.3 g of HCl; with M = 36.458 g/mol that is 440.3 ÷ 36.458 = 12.08 mol/L, the usual quoted figure of about 12 M.
Which percent does the label mean?
A bare "5%" is ambiguous. Solids dissolved in liquids are usually w/v, mixtures of liquids are usually v/v, and concentrated reagents are usually w/w. For dilute aqueous solutions near 1 g/mL the three are nearly equal, but for dense or non-aqueous solutions they are not, so state the type. To dilute a stock of known percent, use the Dilution Calculator.
Common Mistakes
- Using the solvent amount as the denominator. The percent is of the solution. For w/v, dissolve the solute and then make up to the final volume.
- Mixing w/v and w/w. 10% w/v is 10 g in 100 mL of solution; 10% w/w is 10 g in 100 g, which is a different volume when the density is not 1.
- Treating v/v as additive. Always make up to the mark.
- Skipping the density when converting to molarity. A mass percent cannot become a molarity without it; the Molarity Calculator starts from moles instead.
Frequently Asked Questions
- How do you make a percent solution?
- Multiply the percent ÷ 100 by the total amount you want to make. For 500 mL of 0.90% w/v saline that is 4.5 g of NaCl. Dissolve the solute in less than the final volume of solvent, then add solvent up to the final volume.
- What is the difference between w/v, w/w and v/v?
- They differ in what is measured. W/v uses mass of solute per volume of solution (g/100 mL), w/w uses mass per mass (g/100 g), and v/v uses volume per volume (mL/100 mL). The percent is the same arithmetic in each; only the units of the solute and the solution change.
- How do I convert a percent solution to molarity?
- For % w/v, grams per litre is the percent times 10, and dividing by the molar mass gives mol/L: 0.90% NaCl is 9.0 g/L ÷ 58.44 = 0.154 M. For % w/w multiply by the density as well, because a litre of solution weighs more than 1,000 g.
- Is 1% the same as 1 g per 100 mL?
- Only for % w/v. A 1% w/v solution is 1 g of solute per 100 mL of solution, which is 10 g/L. A 1% w/w solution is 1 g in 100 g of solution, and a 1% v/v solution is 1 mL in 100 mL.
- Can a percent solution be above 100%?
- A % w/w or % v/v cannot, because the solute is part of the solution. A % w/v can in principle, since it compares grams with millilitres: a very dense solution may hold more than 100 g of solute per 100 mL. The calculator rejects values above 100 for w/w and v/v only.
- How is this different from parts per million?
- Percent is parts per hundred and ppm is parts per million, so 1% equals 10,000 ppm. Use the PPM Calculator for trace concentrations such as mg/L in water.